A little basic physics - two years later- a 4.0 liter motor (4 liters displacement per rev) turning at 1000 rpm will move .... 4000 liters per minute of air. Or 141 CFM. At 4000 rpm, it's 565 CFM. So that 170 CFM blower will help at low rpms. Over pressure won't be a probelm from a blower of that kind - they are not designed to generate pressure, just high flow. Dead heading (or trying to deliver higher volume than the motor needs) will just burn a little electricity. The blow might actually contribute to restriction at higher demand rates than it can deliver. A bypass flapper would be ideal, but...I still think the blow is a good idea for around town and crawling.
There are flow losses do to that long run of corregated tubing for sure. When I had my '94, I saw a 2-3 mpg drop on highway with the Mantec installed - Len, interesting you haven't seen that. I basically would run it disconnected unless off road. I also notied a bit of loss of torque - so the 'long straw' effect was real in my experience. It's not as bad at low rpm - losses and restriction will increase with square of air flow rate, blah, blah, blah...